Functional strength measurement in cerebral palsy: feasibility, test–retest reliability, and construct validity

ABSTRACT

Purpose: No instrument exists that measures functional strength in both lower and upper extremities in children with cerebral palsy (CP). Therefore, the functional strength measurement (FSM) was tested for feasibility, test–retest reliability and validity in CP.

Methods: Thirty-seven children with CP (aged 4–10 years, Gross Motor Function Classification System I and II) participated. The most common compensations for CP were described; new item descriptions were standardized, and one item was removed. Test–retest reliability was examined. To measure convergent validity, correlations between the FSM-CP and isometric muscle strength measured with the handheld dynamometer (HHD) were determined.

Results: Test–retest reliability was considered high for all items (intra-class correlation coefficient 0.79–0.95). Significant correlations between the HHD and FSM-CP ranged from r = 0.36 to 0.75.

Conclusion: The FSM-CP is feasible, reliable, and valid to use in children with CP. The FSM-CP can be considered as a helpful tool in clinical practice of physical examination of children with CP.

KEYWORDS:

• Cerebral palsy
• children
• feasibility
• functional strength measurement
• reliability
• validity

Acknowledgments

We would like to thank Kirsten Couwenberg, Marie-Louise Portier-Slebus, and Cristel den Otten for collecting the data, and Femke Reijnders-van Son for her help in making it possible to perform a part of this study at Tolbrug Rehabilitation Centre. Lastly, we are grateful to the children and their parents for participating in this study.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.